Recording medium

ABSTRACT

A recording medium includes a substrate, and a deinking agent incorporated in the substrate, on the substrate in a layer, or both in the substrate and on the substrate in a layer. The deinking agent is chosen from an unsaturated fatty acid having from 19 to 23 carbon atoms and combinations of these unsaturated fatty acids. The deinking agent interacts with an ink having been printed on the recording medium to remove the ink during a deinking process.

BACKGROUND

The present disclosure relates generally to recording mediums.

Recycling processes may be used to regenerate usable cellulose fibersfrom waste papers. Some recycling processes involve a deinking method,where ink is removed from waste paper pulp. In some cases, the deinkingmethod includes applying deinking chemicals to waste paper, whichinteract with and remove ink particles from the paper. Such deinkingprocesses may, in some instances, pose a challenge for the recycling ofsome digitally inked papers.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of examples of the present disclosure willbecome apparent by reference to the following detailed description anddrawings, in which like reference numerals correspond to similar, thoughperhaps not identical, components. For the sake of brevity, referencenumerals or features having a previously described function may or maynot be described in connection with other drawings in which they appear.

FIG. 1 schematically depicts an example of a recording medium;

FIG. 2 schematically depicts another example of a recording medium;

FIG. 3 schematically depicts yet another example of a recording medium;

FIG. 4 is a flow diagram depicting an example of a deinking process;

FIGS. 5A and 5B are schematic representations of handsheets made fromun-deinked pulps (FIG. 5A) and deinked pulps (FIG. 5B), where the pulpswere from a liquid electrophotographic (LEP) print medium and oleic acidwas used as a deinking chemical during pulping;

FIGS. 6A and 6B are schematic representations of handsheets made fromun-deinked pulps (FIG. 6A) and deinked pulps (FIG. 6B), where the pulpswere from an LEP print medium and erucic acid was used as a deinkingchemical during pulping;

FIGS. 7A and 7B are schematic representations of handsheets made fromun-deinked pulps (FIG. 7A) and deinked pulps (FIG. 7B), where the pulpswere from a dye-based ink print medium and oleic acid was used as adeinking chemical during pulping, and FIG. 7C is a schematicrepresentation of a membrane filter showing the presence of dissolvedink left in a flotation tank after pulping and flotation;

FIGS. 8A and 8B are schematic representations of handsheets made fromun-deinked pulps (FIG. 8A) and deinked pulps (FIG. 8B), where the pulpswere from a dye-based ink print medium and erucic acid was used as adeinking chemical during pulping, and FIG. 8C is a schematicrepresentation of a membrane filter showing the presence of dissolvedink left in a flotation tank after pulping and flotation;

FIGS. 9A and 9B are schematic representations of handsheets made fromun-deinked pulps (FIG. 9A) and deinked pulps (FIG. 9B), where the pulpswere from a pigment-based ink print medium and oleic acid was used as adeinking chemical during pulping, and FIG. 9C is a schematicrepresentation of a membrane filter showing the presence of dissolvedink left in a flotation tank after pulping and flotation;

FIGS. 10A and 10B are schematic representations of handsheets made fromun-deinked pulps (FIG. 10A) and deinked pulps (FIG. 10B), where thepulps were from a pigment-based ink print medium and erucic acid wasused as a deinking chemical during pulping, and FIG. 10C is a schematicrepresentation of a membrane filter showing the presence of dissolvedink left in a flotation tank after pulping and flotation;

FIGS. 11A and 11B are schematic representations of handsheets made fromun-deinked pulps (FIG. 11A) and deinked pulps (FIG. 11B), where thepulps were from an offset print medium and oleic acid was used as adeinking chemical during pulping; and

FIGS. 12A and 12B are schematic representations of handsheets made fromun-deinked pulps (FIG. 12A) and deinked pulps (FIG. 12B), where thepulps were from an offset print medium and erucic acid was used as adeinking chemical during pulping.

DETAILED DESCRIPTION

Processes for recycling printed waste papers, in some instances, involveconverting the waste paper into a pulp, and then contacting the pulpwith deinking chemicals. The deinking chemicals interact with the ink,and then separate the ink from the waste paper. This recycling processhas suitably been used for waste papers printed using offset inks, butsome challenges may exist for separating and removing digital inks(e.g., liquid electrophotographic (LEP) or other digitally printed inks)from waste papers. For instance, traditional deinking involves removingink particulates falling within a size range of about 10 microns toabout 100 microns. Some challenges with removing digital ink,particularly digital pigment-based inkjet inks or digital dye-basedinkjet inks, include finding a solution to aggregate the pigmentparticles or the dye molecules into a desired size range, and changingthe particles/molecules physical properties from being too hydrophilicto more hydrophobic. It has been found that some existing deinkingchemicals do not, in some instances, efficiently separate the ink fromfibers of a waste paper. It is believed that the challenge(s) is/aredue, at least in part, to the material composition and/or properties ofthe digital ink, which may, in some instances, adversely interact, ornot at all, with the deinking chemicals used by the recycling mill. Inmany cases, the digital ink cannot be separated and removed from thewaste paper to an extent required for adequate waste paper recycling.

The inventors of the present disclosure have found that digital inks maysuitably and successfully be separated from waste papers by selecting aproper deinking agent. As used herein, a deinking agent is a componentof a substrate or of a layer that is deposited on the substrate, whereasa deinking chemical is a component that is added during the pulpingstage of a deinking process. It is to be understood that examples of thedeinking chemicals disclosed herein may also be used as examples of thedeinking agent. Certain fatty acids (such as those having a carbon chainlength of 18 carbons or less (e.g., oleic acid) or those having a carbonchain length of 24 carbons or more (e.g., nervonic acid)) have beensuccessfully used as a deinking chemical for alkaline deinking of offsetprints. It has been found, however, that these fatty acids are not aseffective for the deinking of other selected digital prints, such as,e.g., deinking of LEP prints and/or thermal inkjet prints. In contrast,it has also been found that erucic acid (which has a carbon chain lengthof 22 carbon atoms) effectively deinks LEP digital prints, as well asother prints, such as digital pigment-based inkjet inks or digitaldye-based inkjet inks and non-digital prints.

It is believed that unsaturated fatty acids having from 19 to 23 carbonatoms or combinations of these unsaturated fatty acids may besuccessfully incorporated into and/or on a substrate as a deinkingagent. Examples of such unsaturated fatty acids include 18-nonadecenoicacid, arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid,erucic acid, and docos-21-enoic acid. When the unsaturated fatty acidhas the chemical formula of C₂₂H₄₂O₂, it is believed that the doublebond may be present at any position along the carbon chain. For example,the C₂₂H₄₂O₂ acid may be erucic acid or docos-21-enoic acid.

Based, at least in part upon the results disclosed herein, it isbelieved that a erucic acid deinking agent may be incorporated into thesubstrate (e.g., between the cellulose fibers of the paper, or as partof a coating layer formed on the paper), and the inventors of thepresent disclosure believe that the erucic acid, when included as partof the substrate, may be effective as a non-liquid deinking agent. As acomponent of the substrate, it is believed that the 19 to 23 carbon atomunsaturated fatty acid deinking agent (e.g., the erucic acid deinkingagent) is within close proximity of the ink during the pulping andflotation stages of a deinking process. This is believed toadvantageously improve deinking of the ink from the underlying substratefor digital prints, as well as for non-digital prints including, e.g.,offset inks. In particular regarding erucic acid, since erucic acidemulsifies with water, it is believed that the incorporation of aminimal amount of the erucic acid into the substrate does not pose anydifficulties during paper manufacturing. It is believed that this isdue, at least in part, to the fact that erucic acid forms a workableemulsion in water, and this emulsion may be easily incorporated into theslurry making up the paper base or the coating formed on the paper base.It is also believed that erucic acid, or any of the 19 to 23 carbon atomunsaturated fatty acids, does not deleteriously affect the integrity ofthe substrate.

Referring now to the figures, one example of the recording medium 10 ofthe present disclosure is schematically shown in FIG. 1. In thisexample, the recording medium 10 includes a substrate 12 and a deinkingagent DA, 14 incorporated into the substrate 12.

The substrate 12 for the medium 10 may be chosen from any raw basecontaining any type of pulp fibers, and may be referred to herein as apulp-based substrate or a cellulose fiber-based substrate. The substrate12 may be made from pulp fibers derived from wood, such as from hardwoodtrees (e.g., deciduous trees (angiosperms) such as birch, oak, beech,maple, and eucalyptus) and/or softwood trees (e.g., coniferous trees(gymnosperms) such as varieties of fir, spruce, and pine, as for exampleloblolly pine, slash pine, Colorado spruce, balsam fir and Douglas fir),and these pulp fibers may be prepared via any known pulping process. Thesubstrate 12 may also be made from fibers derived from non-wood (such asbagasse, straw, and bamboo) or from recycled fibers. The raw base forthe substrate 12 may be made with wood containing fibers, such asthermomechanical pulp (TMP) fibers, chemithermomechanical pulp (CTMP)fibers, refiner mechanical pulp fibers (RMP), ground wood (GW) pulpfibers, and/or the like. Further, the raw base may include one or morefillers and/or binders to control the physical properties of thesubstrate 12. Examples of fillers include carbonates (e.g., groundcalcium carbonate and precipitated calcium carbonate), titanium dioxide,clays (e.g., kaolin clay), silicates, oxides, zeolites, talc, andcombinations thereof. An example of a binder is styrene-butadiene rubber(SBR). The filler and/or binder may be added to the fiber structure ofthe raw base, or may be added inside a size/film press.

In an example, the substrate 12 may include some additives, examples ofwhich include internal sizing agents, dry strengthening agents, wetstrengthening agents, fixers, pH adjusters, and/or coloring agents.Examples of internal sizing agents include fatty acids, metal salts offatty acids, alkyl ketene dimmer emulsification products, epoxidizedhigher fatty acid amides, alkenyl acid anhydride emulsification productsand rosin derivatives, alkylsuccinic acid anhydride emulsificationproducts and rosin derivatives, and/or combinations thereof. Examples ofdry strengthening agents that may be used include anionicpolyacrylamides, cationic polyacrylamides, amphoteric polyacrylamides,polyvinyl alcohol, cationized starch, vegetable galactomannan, and/orcombinations thereof. Wet strengthening agents may, for example, includepolyaminepolyamide epichlorohydrin resins, and fixers may, for example,include water-soluble aluminum salts, aluminum chloride, and/or aluminumsulfate. Further, examples of the pH adjuster include sodium hydroxide,sodium carbonate, and/or sulfuric acid, and examples of coloring agentsinclude pigments, coloring dyes, and/or fluorescent brighteners.

The deinking agent DA, 14 is any unsaturated fatty acid having from 19to 23 carbon atoms or combinations of these unsaturated fatty acids.When the selected unsaturated acid has the chemical formula of C₂₂H₄₂O₂,it is believed that the double bond may be present at any position alongthe carbon chain. In an example, the deinking agent DA, 14 is erucicacid. In the example shown in FIG. 1, the deinking agent DA, 14 isincorporated into the substrate 12 material. The deinking agent DA, 14may be incorporated into the substrate 12 during paper manufacturing,and when incorporated, is distributed throughout the bulk of the formedpaper. For instance, the substrate 12 may be manufactured by forming apaper base by chemically and/or mechanically treating wood pulp (e.g.,via a conventional paper manufacturing process), and then adding thedeinking agent DA, 14 to the paper base. In instances where thesubstrate 12 includes fillers, the deinking agent DA, 14 may be added tothe paper base at the same time the fillers are added, or the deinkingagent DA, 14 may be added in a separate step. In instances where thesubstrate 12 does not include fillers, the deinking agent DA, 14 may beadded by itself once the paper base is formed.

In an example, the amount of deinking agent DA, 14 present in thesubstrate 12 ranges from about 0.2 wt % to about 0.8 wt % of the totalwt % of the substrate 12. This range suitably covers most, if not allwaste paper supplies. It is believed that more than 0.8 wt % of thedeinking agent DA, 14 may be present in the substrate 12, up to about 2wt % of the total wt % of the substrate 12. The higher amount ofdeinking agent DA, 14 may be used, for example, for graphic-gradepapers, where high ink coverage (e.g., more than 50% of the paper iscovered with ink) may occur. It has been found that a minimal amount ofdeinking agent DA, 14 present in the substrate 12 (e.g., from about 0.2wt % to about 2 wt %) is enough deinking agent to effectively interactwith an ink having been printed on the medium 10 (i.e., a print) toremove the ink during deinking. Further, it is believed that the minimalamount of deinking agent DA, 14 may also be incorporated into thesubstrate 12 without deleteriously affecting the paper manufacturingprocess. If higher amounts of the deinking agent DA, 14 were used, forexample, it is believed that the excess deinking agent DA, 14 mayaggregate into larger particulates, and remain in the slurry duringpaper manufacturing.

In an example, the substrate 12 has incorporated therein the deinkingagent DA, 14 and at least one other deinking agent (not shown). It isbelieved that the presence of the other deinking agent further enhancesthe deinking process (e.g., may render the deinking process moreefficient, at least in terms of the amount of time for deinking to takeplace. The other deinking agent(s) are selected from another fatty acid,such as a saturated fatty acid, another unsaturated fatty acid, orcombinations thereof. Examples of the saturated fatty acid that may beused as the other deinking agent include acetic acid, propionic acid,butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid,pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylicacid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid,stearic acid, nonadecylic acid, arachidic acid, heneicosylic acid,behenic acid, tricosylic acid, lignoceric acid, pentacosylic acid,cerotic acid, heptacosylic acid, montanic acid, nonacosylic acid,melissic acid, hentriacontylic acid, lacceroic acid, psyllic acid,geddic acid, ceroplastic acid, hexatriacontylic acid, and combinationsthereof. Examples of other unsaturated fatty acids that may be used asthe other deinking agent include α-linolenic acid, stearidonic acid,eicosapentaenoic acid, docosahexaenoic acid, linoleic acid, γ-linolenicacid, dihomo-γ-linolenic acid, arachidonic acid, oleic acid, eicosenoicacid, nervonic acid, mead acid, and combinations thereof. In an example,the other fatty acid that is used in combination with the deinking agentDA, 14 may be chosen from oleic acid (an unsaturated fatty acid) and/orarachidic acid (a saturated fatty acid). It is to be understood that theother deinking agent may be selected from a single deinking agent (onesaturated fatty acid or one unsaturated fatty acid), a combination oftwo or more saturated fatty acids, a combination of two or moreunsaturated fatty acids, or a combination of one or more saturated fattyacids and one or more unsaturated fatty acids.

In an example, the amount of the other deinking agent present in thesubstrate 12 ranges from about 0.2 wt % to about 2 wt % of the total wt% of the substrate 12, and in another example, the amount of the otherdeinking agent ranges from about 0.2 wt % to about 0.6 wt % of the totalwt % of the substrate 12.

Another example of the recording medium 10′ is schematically depicted inFIG. 2. The medium 10′ includes a substrate 12′, and a layer 16 formedon the substrate 12′. It is to be understood that, as used herein, theterms “formed on”, “disposed on”, “deposited on”, “established on”, andthe like are broadly defined to encompass a variety of divergentlayering arrangements and assembly techniques. These arrangements andtechniques include i) the direct attachment of the layer 16 to anotherlayer (e.g., the substrate 12′) with no intervening layers therebetween,ii) the attachment of the layer 16 to another layer (e.g., substrate12′) with one or more layers therebetween, and iii) the attachment of alayer (other than layer 16) to the substrate 12 (shown in FIG. 1) withone or more layers therebetween, provided that the one layer being“formed on”, “disposed on”, “deposited on”, or “established on” theother layer is somehow supported by the other layer (notwithstanding thepresence of one or more additional material layers therebetween). Theother layer(s) (i.e., not layer 16) may include, for example, a firstcoarse coating layer for plain papers, or a top smooth coating forgraphics papers. In some instances, an adhesive layer may be appliedbetween layers, such as between the layer 16 and the substrate 12′ orbetween a smooth coating and substrate 12. Further, the phrases “formeddirectly on”, “disposed directly on”, “deposited directly on”,“established directly on” and/or the like are broadly defined herein toencompass a situation (s) wherein a given layer (e.g., layer 16) issecured to another layer (e.g., substrate 12′) without any interveninglayers therebetween. Any statement used herein which indicates that onelayer is on another layer is to be understood as involving a situationwherein the particular layer that is “on” the other layer in question isthe outermost of the two layers relative to incoming ink materials beingdelivered by the printing system of interest. It is to be understoodthat the characterizations recited above are to be effective regardlessof the orientation of the recording medium materials underconsideration.

In an example, the substrate 12′ may be the pulp-based or fiber-basedsubstrate material described above. In this example, the substrate 12′has coating layer 16 formed thereon. As such, the recording medium 10′may be referred to as a coated substrate.

The coating layer 16 may include inorganic pigments/fillers (e.g.,calcium carbonate, kaolin clay, etc.), natural or synthetic binders(e.g., styrene butadiene rubber (SBR), polyvinyl alcohol, starches,polyethylene imine, polyamide resins, polyesters, polyurethane aqueousdispersions, polyethylene acrylic acid, or the like, or combinationsthereof), and possibly other additives (e.g., a whitening agent such aszinc oxide, titanium oxide, and aluminum oxide).

In an example, the layer 16 has the deinking agent DA, 14 incorporatedtherein. In another example, the layer 16 has the deinking agent DA, 14and one or more other deinking agents incorporated therein. The one ormore other deinking agents is/are selected from saturated fatty acids,unsaturated fatty acids, or combinations thereof, and examples of theseother deinking agents are provided above.

The medium 10′ may be formed by adding the deinking agent DA, 14 to acombination of the pigment(s)/filler(s) and binder(s) to form arelatively dilute coating layer composition (e.g., the coating layercomposition may contain from about 2 wt % to about 5 wt % solids in anaqueous mixture). This coating layer composition may then be appliedonto a surface of the substrate 12′ to form the layer 16. In an example,the composition is applied to a single surface (e.g., S₁) of thesubstrate 12′, or is applied to both surfaces (e.g., opposed surfacesS₁, S₂) of the substrate 12′. The composition may be applied to thesubstrate 12′ to form the coating layer 16 utilizing a metered-sizepress, a puddle-size press, roll-coating, conventional slot-dieprocessing, blade coating, slot-die cascade coating, curtain coating,rod coating, and/or gravure air knife coating. In an example, thecoating layer composition is applied on the base substrate 12′ via acoating machine, which utilizes a sponge and metering blade combination,followed by heating and/or drying. In some instances, spray-coating,immersion-coating, and/or cast coating techniques may also be used.

In the example medium 10′ shown in FIG. 2, the substrate 12′ does notinclude the deinking agent DA, 14 therein. In yet another example, asshown in FIG. 3, the medium 10″ includes a substrate 12 that has thedeinking agent DA, 14 incorporated therein, and a layer 16 formed on thesubstrate 12. In this example, the layer 16 also has the deinking agentDA, 14 incorporated therein. The example medium 10″ shown in FIG. 3 maybe made by incorporating the deinking agent DA, 14 into the substrate 12during manufacturing as described above, and then the substrate 12 maybe coated with the coating layer composition as described above to formthe layer 16.

The medium 10, 10′, 10″ may be printed on using any suitable ink and anysuitable printing system.

Fibers of the medium 10, 10′, 10″ upon which an ink may be deposited toform a printed medium (or print) may be recycled using a conventionalpaper recycling process. For example, the printed medium may be placedinside a recycling mill, and then the colorant of the ink that wasdeposited on the printed medium may be detached from the fibers of themedium 10, 10′, 10″ to form a deinked pulp. The detaching of thecolorant from the medium 10, 10′, 10″ may be referred to herein as adeinking process, and an example of the deinking process isdiagrammatically shown in FIG. 4. This deinking process includes pulpingthe printed medium having the ink printed on a surface thereof in thepresence of a deinking liquid to form a slurry, as shown by referencenumeral 100. Pulping may be accomplished by introducing the printedmedium into a pulper of the recycling mill, and then chopping theprinted medium up into smaller pieces. In a neutral or near-neutraldeinking process, pulping takes place in the presence of neutral ornear-neutral deinking chemicals (e.g., those chemicals having a pHwithin the range of about 7 to about 8). In an alkaline-based deinkingprocess, pulping takes place in the presence of alkaline-based deinkingchemicals, such as NaOH (an alkalinity modifier), a Na₂SiO₃ solution (analkalinity buffering agent), oleic acid or another suitable acid, andH₂O₂ (a bleaching agent). It is believed that some deinking chemicals(e.g., oleic acid) may not be utilized during pulping due, at least inpart, to the required specifications (e.g., as dictated by the deinkingmethod used) of the recovered pulps for certain final paper products(e.g., tissue paper). It is to be understood that during either theneutral/near-neutral deinking process or the alkaline-based deinkingprocess, water may be added inside the pulper while the printed mediumis chopped, thereby converting the printed medium into a slurry of pulpand ink.

During the pulping process, the deinking agent DA, 14 in and/or on themedium 10, 10′, 10″ interacts with the ink that was printed on themedium 10, 10′, 10″. During this interaction, the ink breaks intosmaller particles that are removable during a flotation process,described below. The inks that may be removed from a printed medium viathe deinking process described herein include LEP inks, pigment-basedinkjet inks, dye-based inkjet inks, and inks for offset printing such aswater-based inks for aqueous flexo offset printing, oil-based inks forsheet-fed offset printing, and solvent-based inks (e.g., those includingtoluene) for roto-gravure offset printing.

Regardless of the deinking process used to make the slurry, upon makingthe slurry, examples of the method include performing a flotationprocess, as shown by reference numeral 102 in FIG. 4. The flotationprocess is used to separate the ink from the slurry.

When a neutral or near-neutral deinking process is used, the slurry isintroduced into a froth flotation cell, and then a collector (e.g., afrother) is introduced into the slurry. One example of a suitablefrother is sodium dodecyl sulfate. The frother facilitates formation offoam which allows the removal of the detached ink particles from thefibers. More particularly, since the frother has an affinity to thenow-detached colorant particles, the colorant particles attach to thefrother foam. The foam has a sufficient yield strength to carry a largedistribution of colorant particles to the top of the froth flotationcell. In an example, air may also be blown into the slurry. The airbubbles lift the colorant particles to the surface of the flotation cellas a thick froth, which may be removed from the cell.

When an alkaline-based deinking process is used, the slurry isintroduced into a froth flotation cell. The flotation process of thisexample may take place in the presence or the absence of a frother.

In some instances, the pulp slurry is screened to remove any materialsthat may be denser than the pulp, such as contaminants or other foreignmatter. In an example, coarse and fine screening may be accomplished,for example, by passing the slurry over or through a screen with varyingslot opening sizes to separate such materials from the slurry, and thesematerials may be caught using another mesh screen.

To further illustrate the present disclosure, examples are given herein.It is to be understood that these examples are provided for illustrativepurposes and are not to be construed as limiting the scope of thedisclosed example(s).

EXAMPLES Example 1

Some saturated fatty acids, mono-unsaturated fatty acids, andpoly-unsaturated fatty acids were tested for deinking LEP inks. Printsamples were formed by printing an LEP ink on different cellulose-basedpapers, where each paper was deinked with a different fatty acid. Theamount of fatty acid utilized ranged from about 0.2% per unit paperweight to about 2.0% per unit paper weight. Printing was accomplishedusing an HP® Indigo 5500 digital press, and the prints were deinkedutilizing a lab-scale deinking set up that applied deinking chemicalsduring the pulping step. The deinking chemicals included the selectedfatty acid, about 0.6 wt % sodium hydroxide, about 1.8 wt % sodiumsilicate, and about 0.7 wt % hydrogen peroxide, the wt % of which iswith respect to the weight of the paper products.

Tables 1 and 2 set forth below provide ink/dirt specks (A, measured interms of the area of specks per unit area) of deinked pulp (DP) for bothink/dirt specks of 50 microns or higher (A₅₀) and ink/dirt specks for250 microns or higher (A₂₅₀), where A₅₀ and A₂₅₀ are each expressed inmm²/m². The ink/dirt specks were determined by analyzing handsheetsusing image analysis algorithm(s) run by a processor, and thealgorithm(s) produced a distribution of speck diameters for thehandsheets analyzed.

TABLE 1 Ink/dirt specks for non-deinked or un-deinked pulps (UP), i.e.,those that did not undergo flotation, and deinked pulps (DP), i.e.,those that underwent pulping and flotation, where saturated fatty acidswere used as deinking agents UP DP A₅₀ A₂₅₀ A₅₀ A₂₅₀ Fatty Acid Formula(mm²/m²) (mm²/m²) (mm²/m²) (mm²/m²) Succinic Acid (C₄H₆O₄₎

  2 × 10⁴ 1.8 × 10⁴  2.2 × 10⁴  2.1 × 10⁴ Lauric Acid (C₁₂H₂₄O₂)

1.75 × 10⁴ 1.5 × 10⁴ 3.22 × 10⁴  2.7 × 10⁴ Palmitic acid (C₁₆H₃₂O₂)

 2.3 × 10⁴ 2.2 × 10⁴  5.4 × 10³  4.9 × 10³ Stearic Acid (C₁₈H₃₆O₂)

 2.1 × 10⁴   2 × 10⁴  3.9 × 10³  3.4 × 10³ Arachidic Acid (C₂₀H₄₀O₂)

  2 × 10⁴ 1.9 × 10⁴ 4.35 × 10³ 3.95 × 10³ Behenic Acid (C₂₂H₄₄O₂)

 2.1 × 10⁴ 1.9 × 10⁴  4.4 × 10³  4.2 × 10³ Lignoceric Acid (C₂₄H₄₈O₂)

2.16 × 10⁴ 2.0 × 10⁴  5.5 × 10³  4.9 × 10³

TABLE 2 Ink/dirt specks for non-deinked or un-deinked pulps (UP), i.e.,those that did not undergo flotation, and deinked pulps (DP), i.e.,those that underwent pulping and flotation, where unsaturated fattyacids were used as deinking agents UP DP A₅₀ A₂₅₀ A₅₀ A₂₅₀ Fatty AcidFormula (mm²/m²) (mm²/m²) (mm²/m²) (mm²/m²) Oleic Acid (C₁₈H₃₄O₂)

8.7 × 10³ 6.6 × 10³  4.4 × 10³ 3.2 × 10³ Erucic Acid (C₂₂H₄₂O₂)

3.8 × 10³ 2.2 × 10³ 186 84 Nervonic acid (C₂₄H₄₆O₂)

9.4 × 10⁴ 8.5 × 10⁴ 2.69 × 10³ 2.4 × 10³

As shown in Table 1 above, as the length of the alkyl chain of thesaturated fatty acids increased from 12 carbons to 20 carbons, theink/dirt specks (i.e., the area of specks per unit area) decreased.Fatty acid having 22 and 24 carbon chain lengths had relatively highink/dirt specks that were not consistent with the decreasing trendexhibited by the other fatty acids. Based on this data, it is believedthat the saturated fatty acids used as deinking agents in and/or on thepaper may suitably be used for neutral or near-neutral deinking ofnon-digital inks; but the saturated acids may not be suitable fordeinking LEP inks.

Further, as shown in Table 2 above, some of the mono-unsaturated fattyacids were found to be very effective for deinking. The ink/dirt specksof oleic acid (which has 18 carbon atoms) were too high (i.e., ink/dirtspecks (A₅₀) were larger than about 4000 mm²/m² after deinking (i.e.,deinked pulps DP)), and there was no noticeable change in the speckcount from un-deinked pulps (UP) to deinked pulps (DP). As such, it isbelieved that oleic acid may be unsuitable as a substrate/papercomponent to achieve effective deinking of LEP inks. The ink/dirt specksof nervonic acid (which has 24 carbon atoms) were too high (i.e.,ink/dirt specks (A₅₀) were larger than about 2000 mm²/m² after deinking(i.e., deinked pulps DP)), even though a noticeable change in the speckcount from un-deinked pulps (UP) to deinked pulps (DP) was observed. Assuch, it is believed that nervonic acid may be unsuitable as asubstrate/paper component to achieve effective deinking of LEP inks.However, erucic acid (which has 22 carbon atoms) was found to beparticularly effective for removing LEP ink/dirt specks. This is true,at least in part, because of the noticeable change (which is at least amagnitude lower) in the ink/dirt specks (A₅₀) from un-deinked pulps (UP)to deinked pulps (DP). Further, after deinking, the ink/dirt specks(A₅₀) for erucic acid was determined to be 186 mm²/m², which issignificantly lower than the 600 mm²/m² threshold value (which is setforth on the European Recycling Paper Council Deinking Scorecard'sParameters). These results indicate that erucic acid may be included inand/or on the substrate/paper to achieve effective deinking of LEP inks.

In examples 2-5, it is noted that the wt % values are with respect tothe weight of the comparative paper sample or the paper sample,whichever is being discussed.

Example 2

FIGS. 5A and 5B are schematic representations of handsheets made fromun-deinked pulps (i.e., those that did not undergo flotation) anddeinked pulps, respectively, of a comparative LEP print medium sample,where the ink was Hewlett Packard EI 4.5 ink and the medium wasSTERLING® ultra Digital™ paper (available from Newpage Corp.,Miamisburg, Ohio). For the comparative LEP print medium sample, oleicacid was used as a deinking chemical. FIGS. 6A and 6B are schematicrepresentations of handsheets made from un-deinked pulps and deinkedpulps, respectively, of an LEP print medium sample, where the ink wasHewlett Packard EI 4.5 ink and the medium was STERLING® ultra Digital™paper (available from Newpage Corp., Miamisburg, Ohio). For the LEPprint medium sample, erucic acid was used as a deinking chemical.

An alkaline-based deinking process was used for the comparative sampleand the sample, respectively. The alkaline-based deinking processesfollowed the protocol as outlined in INGEDE (International Associationof the Deinking Industry) Method 11p. The deinking processes wereaccomplished with deinking chemicals, including about 0.3 wt % sodiumhydroxide and 0.9 wt % sodium silicate. Further, as mentioned above,oleic acid was used as a deinking chemical during the pulping of thecomparative LEP print medium sample and erucic acid was used as adeinking chemical during the pulping of the LEP print medium sample. Inthe respective deinking processes, each of the acids was used in anamount of about 0.8 wt %.

The results obtained for the comparative LEP print medium sampleillustrated that poor deinkability of LEP prints occurred when oleicacid was used as a deinking chemical. As shown in FIG. 5B, thecomparative deinked pulp (DP) ink/dirt specks (A₅₀) was 4403 mm²/m²which was representative of the fact that a significant amount of inkwas still left in the pulp after deinking. The results obtained for theLEP print medium sample illustrated that good deinkability of LEP printsoccurred when erucic acid was used as a deinking chemical. As shown inFIG. 6B, the deinked pulp (DP) ink/dirt specks (A₅₀) was measured to beabout 186 mm²/m², and the deinked pulp (DP) ink/dirt specks (A₂₅₀) wasmeasured to be about 24 mm²/m². This was a significant change from theun-deinked pulp (UP) shown in FIG. 6A, demonstrating that a significantamount of the LEP ink was removed from the pulp during deinking. Infact, so few LEP ink particles were left after deinking, the averagediameter (d_(avg)) could not be measured.

These results further support the conclusion that oleic acid may be anunsuitable paper component to achieve effective deinking of LEP inks andthat erucic acid may be a suitable paper component to achieve effectivedeinking of LEP inks.

Example 3

FIGS. 7A and 7B are schematic representations of handsheets made fromun-deinked pulps (i.e., those that did not undergo flotation) anddeinked pulps, respectively, of a comparative dye-based inkjet printmedium sample, where the medium was COLORLOK® paper (Hewlett-Packard,Co., Houston, Tex.). For the comparative dye-based inkjet print mediumsample, oleic acid was used as a deinking chemical. FIGS. 8A and 8B areschematic representations of handsheets made from un-deinked pulps anddeinked pulps, respectively, of a dye-based inkjet print medium sample,where the medium was COLORLOK® paper (Hewlett-Packard, Co., Houston,Tex.). For the sample dye-based inkjet print medium sample, erucic acidwas used as a deinking chemical. The handsheets in FIGS. 7A-8B wereformed from prints produced using dye-based cyan, magenta, and/or yellowink and/or a black ink including carbon black nanoparticles.

An alkaline-based deinking process was used for the comparativedye-based inkjet print medium sample and the dye-based inkjet printmedium sample. The respective alkaline-based deinking processes followedthe protocol as outlined in INGEDE (International Association of theDeinking Industry) Method 11p. The deinking processes were accomplishedwith deinking chemicals, including about 0.3 wt % sodium hydroxide, 0.9wt % sodium silicate, and 0.7 wt % hydrogen peroxide. As mentionedabove, oleic acid was used as a deinking chemical during the pulping ofthe comparative dye-based inkjet print medium sample and erucic acid wasused as a deinking chemical during the pulping of the dye-based inkjetprint medium sample. In the respective deinking processes, each of theacids was used in an amount of about 0.8 wt %.

The brightness (Y) of the water in the flotation tank both after pulpingand after pulping and flotation was measured for both the comparativesamples and the samples. This was accomplished by taking an opticalmeasurement of the filter pad made from the un-deinked pulp and deinkedpulp utilizing an industry standard process called INGEDE (InternationalAssociation of the Deinking Industry) Method 2, entitled “Measurement ofOptical Characteristics of Pulps and Filtrates from Deinking Processes”.The ink elimination (1E) of the comparative deinked sample the deinkedsample was also measured utilizing the same process, namely INGEDEMethod 2.

A comparison between the comparative sample and the sample was made withrespect to ink elimination (IE) and brightness difference (ΔY). Theresults show that the sample deinked with erucic acid had a higher IE(which was about 43.8% of ink particles removed) than the comparativesample that was deinked with oleic acid (where the IE was about 40.3% ofink particles removed). Further, a much larger brightness difference(ΔY) was observed for the comparative sample deinked with oleic acid(i.e., a ΔY of about 31.7) compared with the sample that was deinkedwith erucic acid (i.e., a ΔY of about 11.7, which was lower than thethreshold value of 18). Based upon these results, it can be concludedthat erucic acid is more effective than oleic acid as a deinkingchemical for dye-based inkjet inks. In turn, it is believed that erucicacid may be incorporated into or onto a paper substrate as an effectivedeinking agent for the deinking of dye-based inkjet inks printed on sucha paper substrate.

FIGS. 7C and 8C, respectively, are representations of a membrane filtermade using the process water obtained i) after deinking of thecomparative dye-based inkjet print medium sample where oleic acid wasused as a deinking chemical and ii) after deinking of the dye-basedinkjet print medium sample where erucic acid was used as a deinkingchemical. The membrane filter is representative of the quality of theprocess water that is left in the tank after pulping and flotation. Morespecifically, about a one liter sample including deinked pulp wascollected from the flotation tank after the flotation cycle wascompleted. The liquid was then passed through a Watman grade 41intermediate pore filter paper using a Buchner Filter. About 100 mL ofthe filtrate from the Buchner filter was collected, and was completelydrained in a vacuum filtration unit with a cellulose nitrate membranefilter (i.e. the membrane filter). The membrane filter was then dried,and was used as a measure of the dissolved ink in the flotation tank.The darker color shown in the membrane filter (MF) for the comparativeprint sample including oleic acid (FIG. 7C) illustrates that too muchcolor (i.e., the presence of the ink particles) was left in the waterafter deinking, and thus the water could not be reused for anotherdeinking process. In contrast, the membrane filter for the print samplethat used the erucic acid deinking chemical was substantially clear (seeFIG. 8C), indicating that the water did not have as much ink remainingand was reusable.

Example 4

FIGS. 9A and 9B are schematic representations of handsheets made fromun-deinked pulps (i.e., those that did not undergo flotation) anddeinked pulps, respectively, of a comparative pigment-based inkjet printmedium sample, where the medium was COLORLOK® paper (Hewlett-Packard,Co., Houston, Tex.). For the comparative pigment-based inkjet printmedium sample, oleic acid was used as a deinking chemical. FIGS. 10A and10B are schematic representations of handsheets made from un-deinkedpulps and deinked pulps, respectively, of pigment-based inkjet printmedium samples, where the medium was COLORLOK® paper (Hewlett-Packard,Co., Houston, Tex.). For the pigment-based inkjet print medium sample,erucic acid was used as a deinking chemical. The handsheets in FIGS.9A-10B were formed from prints utilizing pigment-based inks for the HP®Edgeline printer (available from Hewlett-Packard Co., Houston, Tex.).

An alkaline-based deinking process was used for the comparativepigment-based inkjet print medium sample and the pigment-based inkjetprint medium sample, respectively. The respective alkaline-baseddeinking processes followed the protocol as outlined in INGEDE(International Association of the Deinking Industry) Method 11p. Thedeinking processes were accomplished with deinking chemicals, includingabout 0.3 wt % sodium hydroxide, 0.9 wt % sodium silicate, and 0.7 wt %hydrogen peroxide. Further, as mentioned above, oleic acid was used as adeinking chemical during pulping of the comparative pigment-based inkjetprint medium sample and erucic acid was used as a deinking chemicalduring pulping of the pigment-based inkjet print medium sample. In therespective deinking processes, each of the acids was used in an amountof about 0.8 wt %.

The brightness (Y) of the water in the flotation tank both after pulpingand after pulping and flotation was measured for both the comparativepigment-based inkjet print medium sample and the pigment-based inkjetprint medium sample. The brightness (Y) was measured utilizing INGEDEmethod 2 mentioned above. The ink elimination (IE) of the comparativedeinked sample the deinked sample was also measured utilizing INGEDEmethod 2.

A comparison between the comparative pigment-based inkjet print mediumsample and the pigment-based inkjet print medium sample was made withrespect to ink elimination (IE) and brightness difference (ΔY). Theresults show that the sample deinked using erucic acid as a deinkingchemical had a higher ink elimination (which was about 71.5% of inkparticles removed) than the comparative sample that was deinked usingoleic acid as a deinking chemical (where the IE was about 43.4% of inkparticles removed). Further, a much larger brightness difference (ΔY)was observed for the comparative pigment-based inkjet print mediumsample that was deinked with oleic acid (i.e., a ΔY of about 35)compared with the pigment-based inkjet print medium sample that wasdeinked with erucic acid (i.e., a ΔY of about 9.9, which again was lowerthan the threshold value of 18). Based upon these results, it can beconcluded that erucic acid is more effective than oleic acid as adeinking chemical for pigment-based inkjet inks. In turn, it is believedthat erucic acid may be incorporated into or onto a paper substrate asan effective deinking agent for the deinking of pigment-based inkjetinks printed on such a paper substrate.

FIGS. 9C and 10C, respectively, are representations of a membrane filtermade using the process water from i) the deinking of the comparativepigment-based inkjet print medium sample using oleic acid as a deinkingchemical and ii) the deinking of the pigment-based inkjet print mediumsample using erucic acid as a deinking chemical. These membrane filterswere formed and treated in the same manner as the membrane filtersdescribed in Example 3. The darker color shown in the membrane filterfor the comparative pigment-based inkjet print medium sample deinkedusing oleic acid (FIG. 9C) illustrates that too much color (i.e., inkparticles) was left in the water after deinking, and thus the watercould not be reused for another deinking process. In contrast, themembrane filter for the pigment-based inkjet print medium sample deinkedusing erucic acid was substantially clear (see FIG. 10C), indicatingthat the water did not have as much ink remaining and was reusable.

Example 5

FIGS. 11A and 11B are schematic representations of handsheets made fromun-deinked pulps (i.e., those that did not undergo flotation) anddeinked pulps, respectively, of comparative coldset web offset mattepaper samples, where the medium was matte coated paper. For thiscomparative sample, oleic acid was used as a deinking chemical. FIGS.12A and 12B are schematic representations of handsheets made fromun-deinked pulps and deinked pulps, respectively, of coldset web offsetmatte paper samples, where the medium was matte coated paper. For thissample, deinking was accomplished using erucic acid as a deinkingchemical. The handsheets in FIGS. 11A-12B were formed from printsutilizing offset inks.

An alkaline-based deinking process was performed for the comparativecoldset web offset matte print medium sample and the coldset web offsetmatte print medium sample. The alkaline-based deinking processesfollowed the protocol as outlined in INGEDE (International Associationof the Deinking Industry) Method 11p. The respective deinking processeswere accomplished with deinking chemicals, including about 0.3 wt %sodium hydroxide, 0.9 wt % sodium silicate, and 0.7 wt % hydrogenperoxide. Further, as mentioned above, oleic acid was used as a deinkingchemical during the pulping of the comparative coldset web offset matteprint medium sample and erucic acid was used as a deinking chemicalduring the pulping of the coldset web offset matte print medium sample.In the respective deinking processes, each of the acids was present inan amount of about 0.8 wt %.

The results obtained for the comparative coldset web offset matte printmedium sample and the coldset web offset matte print medium sampleillustrate adequate deinkability of offset prints when either oleic acidor erucic acid was used as a deinking chemical during deinking. This isshown in both FIGS. 11B and 12B for oleic acid and erucic acid deinkedsamples, respectively.

From Examples 2 through 5 above, it was found that erucic acid may beused as a suitable deinking chemical during pulping for the removal ofLEP inks, dye-based inks, pigment-based inks, and offset inks fromvarious papers. Based on these results, it is believed that the erucicacid will also perform in the same way when the fatty acid is introducedinto and/or onto the paper as a deinking agent. Erucic acid will becloser in proximity to the inks when incorporated into and/or onto thepaper, and thus it is believed that the deinking results for theseexamples may be even better than the deinking results reported herein.

Example 6

Table 3 shows the European Recycling Paper Council's deinking score cardresults for the comparative deinked samples and deinked samples of eachof Examples 2-5. The first section of Table 3 illustrates the EuropeanRecycling Paper Council's deinking score card parameters; and thesubsequent sections of Table 3 illustrate the scores for the variousExamples 2-5.

TABLE 3 European Recycling Paper Council Deinking Scorecard Results ofComparative Samples and Samples in Examples 2-5 Color Ink FiltrateOptical Shade, Dirt, A₅₀ Dirt, A₂₅₀ Elimination, Darkening, TotalBrightness, Y a* (mm²/m²) (mm²/m²) IE (%) ΔY Score European RecyclingPaper Council Deinking Scorecard's Parameters Threshold 47 −3/+2 2000600 40 18 100 Target 90 −2/+1 600 180 80 6 Max 35 20 15 10 10 10 ScoreComparative Examples with Oleic Acid Example # 2 33 20 −15 −10 10 10Fail 3 26 20 15 10 1 −10 Fail 4 17 20 15 10 1 −1 Fail 5 35 20 15 10 1010 100 Examples with Erucic Acid 2 35 20 15 10 10 10 100 3 17 20 15 10 15 68 4 35 19 15 10 10 7 96 5 35 20 15 10 10 10 100

It is to be understood that a total score of 70 on the EuropeanRecycling Paper Council's deinking score card is considered to be gooddeinkability.

In Table 3, any print sample that failed any category (e.g., A₅₀, ΔY,etc.) (which is shown by the term “fail” in the total score in thetable) means that the print sample could not be properly deinkedutilizing the INGEDE Method 11p deinking method, and is considered to beunsuitable for deinking. As shown in Table 3, deinking may beaccomplished for all four of the papers utilizing the erucic aciddeinking agent in the paper, whereas it was found that for comparativeexamples 2-4, incorporation of oleic acid into the paper does not meetpassing standards stipulated for the INGEDE method 11p. In fact, it wasfound that of all of the comparative examples, only the offset paper(comparative example 5) may be properly deinked utilizing the oleic aciddeinking agent as a component of the paper.

It is to be understood that the ranges provided herein include thestated range and any value or sub-range within the stated range. Forexample, a range from about 0.2 wt % to about 2 wt % should beinterpreted to include not only the explicitly recited limits of about0.2 wt % to about 2 wt %, but also to include individual values, such as0.2 wt %, 0.7 wt %, 1 wt %, etc., and sub-ranges, such as from about 0.5wt % to about 1 wt %, from about 0.75 wt % to about 1.6 wt %, etc.Furthermore, when “about” is utilized to describe a value, this is meantto encompass minor variations (up to +/−10%) from the stated value.

While several examples have been described in detail, it will beapparent to those skilled in the art that the disclosed examples may bemodified. Therefore, the foregoing description is to be considerednon-limiting.

What is claimed is:
 1. A recording medium, comprising: a substrate; anda deinking agent incorporated: i) in the substrate; ii) on the substratein a layer; or iii) both i and ii, the deinking agent being chosen froman unsaturated fatty acid having from 19 to 23 carbon atoms andcombinations of these unsaturated fatty acids; wherein the deinkingagent is to interact with an ink having been printed on the recordingmedium to remove the ink during a deinking process.
 2. The recordingmedium as defined in claim 1 wherein the unsaturated fatty acid has achemical formula of C₂₂H₄₂O₂, and wherein a double bond of the C₂₂H₄₂O₂is present at any position along its carbon chain.
 3. The recordingmedium as defined in claim 2 wherein the unsaturated fatty acid iserucic acid.
 4. The recording medium as defined in claim 1 wherein theunsaturated fatty acid is present in an amount ranging from about 0.2 wt% to about 2 wt % per unit weight of the substrate.
 5. The recordingmedium as defined in claim 1, further comprising an other deinking agentchosen from a saturated fatty acid, an other unsaturated fatty acid, andcombinations thereof.
 6. The recording medium as defined in claim 5wherein: the saturated fatty acid is chosen from acetic acid, propionicacid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylicacid, pelargonic acid, capric acid, undecylic acid, lauric acid,tridecylic acid, myristic acid, pentadecanoic acid, palmitic acid,margaric acid, stearic acid, nonadecylic acid, arachidic acid,heneicosylic acid, behenic acid, tricosylic acid, lignoceric acid,pentacosylic acid, cerotic acid, heptacosylic acid, montanic acid,nonacosylic acid, melissic acid, hentriacontylic acid, lacceroic acid,psyllic acid, geddic acid, ceroplastic acid, and hexatriacontylic acid;and the other unsaturated fatty acid is chosen from α-linolenic acid,stearidonic acid, eicosapentaenoic acid, docosahexaenoic acid, linoleicacid, γ-linolenic acid, dihomo-γ-linolenic acid, arachidonic acid, oleicacid, eicosenoic acid, nervonic acid, and mead acid.
 7. The recordingmedium as defined in claim 1 wherein the recording medium includes thelayer, which has the deinking agent incorporated therein.
 8. Therecording medium as defined in claim 7 wherein the layer further has another deinking agent therein, the other deinking agent chosen from asaturated fatty acid, an other unsaturated fatty acid, or combinationsthereof.
 9. The recording medium as defined in claim 1 wherein thesubstrate is chosen from a base paper including cellulose fibers.
 10. Amethod for forming the recording medium as defined in claim 1,comprising incorporating the deinking agent into the substrate by:forming a paper base by any of chemically or mechanically treating woodpulp; and adding the deinking agent to the paper base.
 11. A method forforming the recording medium as defined in claim 1, comprising: addingthe deinking agent to a combination of a pigment and a binder to form acoating layer composition; and applying the coating layer compositiononto a surface of the substrate to form the layer.
 12. A deinkingprocess, comprising: pulping a medium having an ink printed on a surfacethereof in the presence of a deinking chemical to form a slurry, themedium having a deinking agent that is: i) incorporated into the medium;ii) incorporated into a layer formed on a surface of the medium; or iii)both i and ii, the deinking agent being chosen from an unsaturated fattyacid having from 19 to 23 carbon atoms and combinations of theseunsaturated fatty acids; and performing a flotation process using theslurry and a frother.
 13. The deinking process as defined in claim 12wherein the deinking agent, upon interacting with the ink during thepulping process, breaks the ink into smaller particles that areremovable during the flotation process, and wherein the ink is chosenfrom liquid electrophotographic (LEP) inks, pigment-based inkjet inks,dye-based inkjet inks, and inks for offset printing.
 14. The deinkingprocess as defined in claim 12 wherein the medium further includes another deinking agent in combination with the deinking agent, the otherdeinking agent chosen from a saturated fatty acid, an other unsaturatedfatty acids, and combinations thereof.
 15. The deinking process asdefined in claim 12 wherein the deinking chemical is a mixture of sodiumhydroxide, sodium silicate, and hydrogen peroxide.